The aims are to organize and conduct a conference in October, 1994 bringing together researchers of varied background on the subject of motor proteins, and to produce a reference work on the subject. The discussion will be focused on the mechanism by which these molecules use chemical energy to perform mechanical work. Several recent advances in this field make this a propitious time for a conference on this subject. These include the elucidation of the structures of actin and of the head region of myosin, the observation of the unitary step for kinesin and the unitary force for myosin, and the development of genetic approaches for both the myosin family and the kinesin family of motors. The discussions will examine in detail the function of the actin based motors, the microtubule based motors and the bacterial rotary motor. In addition, the function of other proteins that produce motion in cells, such as nucleic acid polymerases will also be explored. The topics for each motor system will include; (a) where known, the structures of the proteins, along with the changes in structure required for energy transduction; (b) the mechanics, measured in organized systems and in in vitro assays of either small numbers or single motors; (c) the kinetics and energetics of the interactions measured in solution and in organized systems and (d) the cloning, expression and functional characterization of native and mutant forms of the proteins. From their beginnings over 10 years ago, the intent of the Biophysical Discussions has been to discuss areas that have been heavily influenced by biophysical approaches. They employ a unique format whereby: (a) complete texts of all contributions are circulated in advance to all participants; (b) The meeting time is devoted solely to discussions,not to formal presentations; (c) a transcript of the plenary debate is incorporated into the final proceedings volume. Fifteen to twenty full Discussion papers will be solicited by invitation. Some 40 more two-page papers will be invited for presentation in plenary poster sessions. The transcribed proceedings of the Biophysical Discussions will be published as the seventh in a series of hardbound Biophysical Discussions volumes. The identical text, consisting of plenary papers, two-page summaries of the poster presentations, and edited transcripts of the plenary debates, all fully indexed, will be published simultaneously as the may, 1995 issue of the Biophysical journal, thus ensuring prompt distribution, easy reference and general accessibility. An international Call for Abstracts to be submitted in May, 1994, will be made by announcements in journals and circulars sent to members of professional organizations.